1. Field of the Invention
The present invention relates to a synchronous rotating type scroll member fluid machine of the type in which a pair of scroll members are synchronously rotated by corresponding motors so as to compress gas in a scroll member working chamber, which may be used as a compressor of a refrigerator or air conditioner.
2. Description of the Prior Art
Conventional scroll member fluid machines have been described in, for example, Japanese Patent Unexamined Publication Nos. 61-20391, 1-200083 and 2-149783.
Among the above conventional techniques, Japanese Patent Application Laid-Open No. 61-200391 discloses a vertical scroll member compressor which includes a fixed scroll member 1, an orbiting scroll member 2, a rotary shaft 3 provided with a crank shaft, a casing and so on, as shown in FIGS. 20 and 21. FIG. 20 is a partial cross-sectional view of an upper portion of the rotary shaft 3, and FIG. 21 is a partial cross-sectional view of a lower portion of the rotary shaft 3. Between the portions respectively shown in FIGS. 20 and 21 is disposed a motor (not shown). The interior of the rotary shaft 3 also serving as the motor shaft is made hollow, and a cylindrical member 4 is disposed in the hollow portion, by which a double cylindrical space is formed. A fitting 5 having an outlet and an inlet for a cooling water 6 is disposed at the lower end of the rotary shaft 3, and the cooling water 6 is circulated within the double cylindrical space so as to cool the motor or the like.
FIG. 22 shows the scroll member compressor disclosed in Japanese Patent Unexamined Publication No. 1-200083. In this scroll member compressor, a pair of scrolls 7 and 8 in a casing C are respectively coupled to motor shafts 9 and 10 rotatably supported by the casing C, which are respectively rotated by first and second motors 11 and 12 fixed to the casing C. Sensors 13 and 14 are provided so as to detect the rotating state of the two rotary shafts 9 and 10. A control device 16 drives a third motor 15 on the basis of the signals obtained by the sensors 13 and 14 such that the rotational phase difference between the two rotary shafts 9 and 10 is reduced. A space 17 within the casing C forms a suction chamber. The interior of the motor shaft 9 is made hollow, and the hollow portion forms a discharge flow passage 18 partially having a discharge port 18'. A gas which enters the casing C in the manner indicated by arrow A is sucked from the scroll member outer peripheral portion and is compressed as it moves toward the center of the scroll member. A resultant high-pressure gas passes through the discharge flow passage 18 in the motor shaft 9 and then the discharge port 18' and is discharged outside of the compressor.
FIG. 23 shows the scroll member compressor disclosed in Japanese Patent Unexamined Publication No. 2-149783. This scroll member compressor has a pair of rotatable scroll members 7 and 8. The scroll member 8 is coupled to a motor shaft 19, and the other scroll member 7 is rotatable supported by a shaft on a holder 20. Rotation of the scroll member 8 driven by the motor shaft 19 rotates the scroll member 7 through an Oldham's mechanism 20'. A compression mechanism portion, including the scrolls 7 and 8, a motor 21 and a lubricating oil 43 are accommodated in a hermetic casing 22. A lower space where the motor 21 is accommodated forms a suction chamber space 23, and a space separated from the lower space by the holder 20 and a frame 25 serves as a discharge chamber space 24. The frame 25 for rotatably supporting the motor shaft has a flow passage 25' for the suction gas which is communicated with a suction space 29 on the scroll member outer peripheral portion. In the center of the scroll member 7 is provided a rotary shaft 26 having a discharge flow passage, which is opened to the discharge space 24 at the end portion of the rotary shaft 26. The rotary shaft 26 is rotatably supported on the holder 20. Between the holder 20 and the scroll member 7 is provided a back pressure chamber 27 in which the discharge gas is led from the discharge space 24 in a sealing state. The gas force in the back pressure chamber 27 and the thrust gas force in the compression working chamber formed by the two scroll member meet with each other. The back pressure space 27 and the suction space 29 located on the outer side of the suction space 27 are separated from and sealed to each other by a projecting portion 28 provided on the holder 20.
The aforementioned conventional scroll member compressors have the above structure so as to provide the following drawbacks. In the technique disclosed in, for example, Japanese Patent Unexamined Publication No. 61-200391, the cooling water 6, which is different from the working gas, is supplied into the inner space of the double cylindrical portion 4 provided in such a manner that it passes through the motor shaft 3. The supplied cooling water is returned through the outer space of the double cylindrical portion 4. Consequently, in a normal operating state, the motor can be effectively cooled from inner side thereof. However, in order to maintain the motor temperature to an appropriate value when the load applied to the motor changes to a great degree, the amount of cooling water must be controlled by providing a valve (not shown), such as a throttle valve, in the cooling water pipe and by opening or closing the opening thereof according to the load applied to the motor. To control the flow rate of the cooling water according to the load and thereby maintain the motor temperature to an appropriate value, i.e., to automatically change the motor cooling ability according to the load applied to the motor or cooling the motor by the working gas which flows in the scroll member wrap, have not been given much consideration in the conventional technique.
Japanese Patent Unexamined Publication No. 1-200083 discloses the structure of discharge flow passage in the scroll member compressor of the type in which one pair of scrolls are rotated. However, the discharge flow passage is formed only in the motor shaft 9. Furthermore, the discharge flow passage is not formed so as to pass through the whole motor shaft 9. Thus, the motor cannot be cooled by the working gas, and consideration is not given fully to the cooling of the motor when the load to the motor varies. Furthermore, in the motor shaft 9, a reacting force to be exerted to the scroll member is generated due to flow of the high-pressure discharge gas. However, such a dynamic reaction is not generated in the other shaft because no flow passage is provided therein. Consequently, thrusts having different magnitudes are exerted to the two scrolls 7 and 8 and a thrust is thus exerted to the forward surface of the wrap of each of the scrolls. In that state, if the two scroll members are synchronously rotated at a high speed in that state, dynamic loss due to friction or burning of the wraps and hence disability of the operation of the compressor may occur. Thus, to achieve high-speed operation, balancing of the thrusts is essential. However, in the aforementioned conventional technique, no consideration is given to synchronous high-speed rotation of the two scroll members in a state wherein the thrusts exerted thereto are balanced.
In the technique disclosed in Japanese Patent Unexamined Publication No. 2-149783 in which the two scroll members are rotated by the single motor, the through-hole is formed in the driving shaft of one of the scroll members, and the technique for balancing the thrusts exerted to the scroll members has been proposed. That is, in order to obtain such balanced thrusts, the back pressure space 27 is provided between the scroll member 7 and the holder 20 and a discharge gas is led into the back pressure space 27. However, since the back pressure space 27 has a fixed area and the inner pressure thereof is the discharge pressure, the thrust exerted to the scroll member 7 is fixed. Thus, when the thrust in the compression chamber varies due to changes in the suction pressure, the inner pressure of the back pressure space and the pressure in the compression working chamber may be imbalanced. It is thus difficult to always obtain desired thrusts. Furthermore, the sealing portion 28 is disposed on the rear surface of the rotary scroll member 7 to separate the back pressure space 27 from the suction pressure in the outer peripheral portion of the scroll member. However, this sealing is performed between the scroll member 7 which is a rotary member and the holder 20 which is a stationary member, and gas leakage cannot thus be avoided. The leaking gas is mixed into the suction gas, thus reducing the flow rate thereof and hence deteriorating the performance of the compressor. The amount of gas which leaks may be reduced by increasing the contact pressure of the sealing portion 28. However, in that case, frictional loss due to sliding increases as the rotational speed increases, and the performance of the compressor is thus deteriorated. Furthermore, in this technique, since one of the scroll members is rotated by the motor while the other scroll member is rotated by means of the Oldham's mechanism 20' disposed between the two scroll members, when the suction pressure changes and the thrust is exerted to the Oldham's mechanism 20', a frictional loss increases.
Another conventional synchronous rotating type scroll member fluid machines are disclosed in, for example, Japanese Patent Unexamined Publication No. 64-302. In the first scroll member of this fluid machine, a drive member for rotating a second scroll member is slidably disposed on the rear surface of the end plate of the first scroll member opposite to a vertical surface for providing the wrap in addition to the rotary shaft, and only the scroll member wrap is provided on the front surface of the end plate of the first scroll member. In the conventional technique disclosed in, for example, Japanese Patent Unexamined Publication No. 1-267379, a drive member for rotating the second scroll member is slidably disposed between the scroll end plates of the first and second scroll members, and only the motor shaft is provided on the rear surface of the end plate of the first scroll member opposite to the surface in which the wrap is vertically provided.
In the aforementioned conventional synchronous rotating type scroll member fluid machines, since the scroll member is rotated, a centrifugal force is exerted to the scroll member wrap, deforming the wrap outwardly in the radial direction. The force and deformation thereof increase as the distance from the center of the wrap increases. Since the end plate and the scroll member wraps are formed as one unit in the scroll member, the centrifugal force generated by the scroll wrap acts to the scroll end plate as a moment load. In the aforementioned conventional techniques, since the outer peripheral portion of the scroll end plate of each of the scroll members is not supported in the thrust direction, the scroll end plate may be deformed by the moment load in an arc in which the wrap side surface thereof is protruded outerward thereof. In that case of generating such a deformation, the two scroll end plates move closer to each other at the central portion of the scroll members, increasing the slide frictional loss which may lead to contact of the end plates in the worst case. Furthermore, since the outer peripheral portions of the end plates move away from each other, the gap in the axial direction between the scroll member wrap and the surface of the scroll end plate increases, while the gap in the radial direction between the side portions of the two scroll wraps becomes non-uniform. This may lead to contact of the side surfaces of the scroll wraps. In the aforementioned conventional techniques, as the rotational speed of the scroll members increases, the possibility of the deformation increases, thus increasing contact between the scroll members. Consequently, vibrations and noise levels are increased and damage to the parts is generated. These deteriorate reliability of the compressor.
An increase in the gap between the scroll wraps is mainly caused by the scroll end plate rather than the scroll wraps themselves. Hence, a thicker and more rigid end plate may be used to decrease the deformation thereof and thereby decrease the gap between the scroll wraps. However, the scroll end plate has a disk-like form and is hence less rigid against an out-of-plane force applied thereto. Therefore, it must have a large thickness as compared with the wrap. In that case, however, the weight and, hence, inertial mass of the scroll member is increased, and the scroll member may not follow rotation of the motor excellently when the motor is activated or stopped. This makes synchronous rotation of the motors difficult.